1. Field of the Invention
This invention relates to a knitted fastener material and apparatus and method of producing the fastener material.
2. Description of the Prior Art
Separable fasteners such as those described in U.S. Pat. Nos. 2,717,437 and 3,009,235 which are marketed under the registered trademark VELCRO brand hook and loop fasteners by Velcro USA Inc., 681 Fifth Avenue, New York, N.Y. have gained wide acceptance because of the properties of the mating hooks and loops which permit their attachment by merely placing a surface defined by the hooks into face-to-face relationship with a surface defined by the loops so that a large number of hooks engage a large number of loops which resist separation parallel to the interfacial plane of engagement but are readily separable by peeling forces applied substantially normal to this interfacial plane. These fastening devices are generally formed of a sheet of woven or knitted fabric having raised threads of synthetic material, such as nylon, which are napped or unnapped, to provide a pile surface defined by a plurality of loops, and which may be thermally treated to become semi-rigid. Certain of the loops may then be cut along one side near their outer extremity to form hooks.
More recently, proposals have been advanced to produce hook and loop fasteners using techniques other than weaving. For example, hook-type fasteners have been molded of synthetic plastic materials and both hook and loop-type fasteners have been knitted of textile filamentary yarn materials.
Of the knitted fastener materials, attempts have been made to construct the fabric on raschel knitting machines as well as circular knitting machines. For the raschel knitting machines a serious problem was presented in properly guiding the yarn filamentary materials to the knitting zones in a manner to form pile-like members upstanding from the base knitted fabric so as to provide a suitable fabric material for ultimate use as part of a separable fastener material. For the circular knitting devices, it was found to be unusually difficult to utilize pile-forming lancets in connection with rotary sections of the machinery and to cause to be constructed the precise basic fabric having upstanding pile members which could be used as part of a separable fastener of the type contemplated herein. Additionally, difficulties were encountered in the production of hook-type elements from pile loop members wherein it was necessary to cut the loop members so as to form hooks which would be suitable for interengagement with a fastener fabric having a multiplicity of loop members upstanding from a basic fabric.
Aside from the above difficulties of developing a suitable apparatus from which could be constructed a base fabric having a multiplicity of hooking elements upstanding therefrom, as heretofore mentioned, the preciseness required to cut a multiplicity of monofilamentary loop members so as to form hook members has always been considered to be a relatively expensive technological development. In an effort to reduce the cost of producing such hooking elements, several developments have more recently concentrated upon the production of hook-type hooking elements having a well-known mushroom-like configuration, as opposed to the classical hook. However, such fastener materials have exhibited disadvantages peculiar to their production and configuration. As one example, it has been found that as compared to a material having hook-type hooking elements upstanding therefrom, the materials having mushroom hooking elements have been found to be capable of withstanding greater shear forces when engaged with a mating material having a plurality of loop members upstanding from one surface; however, the peel forces required to separate the mushroom fastener fabric from the loop member is also greater than the forces required to separate the classical hook fabric, while destruction of the loop members by the mushroom members is more rapid than that of the classical hook-type fabric. The end result of this phenomenon is that the cycle life of the mushroom/loop fastener device is significantly lower than that of the classical hook/loop cycle device.
While numerous reasons for this phenomenon have been advanced, a plausible theory concentrates on the constructional distinctions between the classical hook-type hooking element and the mushroom-type hooking element. These distinctions will lead a person ordinarily skilled in the art to conclude that the hook-type hooking element is more flexible by virtue of its reduced constructional mass as compared to the mushroom-type hooking element.
Raschel knit fastener fabrics and devices to produce these fabrics are disclosed in U.S. Pat. Nos. 3,539,436 and 3,530,687, both to Hamano. On the other hand, a method and apparatus for producing a circular knitted fastener fabric is disclosed in U.S. Pat. Nos. 3,765,193 to Conroux et al., 3,845,640 and 3,845,641, both to Waller, while a circular knit fastener fabric having projecting barbs is disclosed in U.S. Pat. No. 3,654,054 to Waller.
Examples of mushroom-type separable fastener fabrics may be found in U.S. Pat. Nos. 3,138,841 and 3,320,649, both to Naimer. U.S. Pat. Nos. 3,718,725 and 3,770,359, both to Hamano, disclose a method and apparatus for the manufacture of hook fabric material for fasteners wherein the hook elements have a general constructional configuration resembling the well-known mushroom. U.S. Pat. No. 3,266,113 to Flanagan, Jr., relates to a fastener having interacting unitary engageable articles disclosed for the engagement which complementary members are pressed together and disengagement upon separation.
While these developments have provided several generations of press and peel type fastener devices, the difficulties associated with their manufacture as well s those associated with their functioning abilities and fastening capabilities have provided some disadvantages in their regard, particularly when the cost of production is considered. We have invented a fastener of weft knitted material and an apparatus and method of producing the same, which combines the fastening capabilities of mushroom, with peel flexibility of hook, thereby resulting in an extremely effective fastening material. Moreover, our apparatus and method of producing this material provides a heretofore unknown inexpensive technique for constructing a superior weft knitted quasi-hook/quasi-mushroom fastener material in a single location from the yarn stage to the circular knit tube slitting stage, thus providing an alternative to the difficulties and disadvantages associated with the prior art devices.